Teenagers could take GCSEs early and have a year without examinations before starting A levels, under far-reaching reforms set out yesterday.

The biggest shake-up of the qualification since it was introduced will make the GCSE structure overwhelmingly modular. Each unit will be assessed as soon as it is completed, with pupils allowed one chance to retake any module they fail.

Critics are expected to claim that this will make it almost impossible for teenagers not to achieve good grades.

Pupils in their early teens will be encouraged to start GCSEs before the usual age of 14: the new modular system will make it simpler for talented younger students to take units.

Candidates will no longer be able to take coursework projects home – instead they will complete “controlled assessment” in the classroom.

Examinations will also feature more varied types of questions, giving room for extended writing and analysis in candidates’ answers.

Officials have updated 60 subjects for pupils starting GCSEs in September 2009. The core subjects of English, mathematics and IT will be revamped the year after.

The history syllabus is to include the study of terrorism. Religious studies will give more recognition to Sikhism and Buddhism, to reflect greater representation of those faiths in the classroom, and includes humanism for the first time.

Geography pupils will be taught that “sustainable development is a key strategy for the survival of the planet and its people”.

Teenagers taking the music GCSE will have the chance to be assessed on rapping, dance music and freestyle DJing.

Schools will be able to introduce modular versions of most courses, dividing the qualification into multiple chunks that are assessed after each part. Greg Watson, chief executive of OCR, one of the main awarding bodies, said: “We don’t want the exam system to be the one thing that slows people down. Some schools might stick to having a final exam at 16, because they won’t want the disruption of going modular.

“But there is growing evidence that schools are looking at personalised learning: students could start some GCSEs in Year 9 [when aged 13] and finish them at the end of Year 10. Then they could start doing A levels a year early. Or they could treat Year 11 as a bridging year and take time out from exams to do more exploration, or do preparatory courses for A levels.”

The intention was not for pupils to accrue 15 GCSEs by sitting for them two years running. “I hope the tide has turned against that,” Mr Watson said. “The GCSE is an important staging post – it’s a stepping stone rather than the school-leaving certificate it was 20 years ago.

“Having units lets people build up in their own time.

“This would free up time for the last three years of school [to be used] either as a broader curriculum or to concentrate on A levels. There is concern about the jump from GCSEs to A levels, which is a shock for some young people.”

Defending the modular system, which allows pupils to gain qualifications without their having to commit to memory vast tracts of information, Mr Watson said: “There’s been a move away from rote learning and repetition towards using data and processing it.”

Details of the new GCSEs were announced by Ofqual, the examinations regulator. Kathleen Tattersall, who chairs Ofqual, said: “These new GCSEs will ensure that all young people are able to demonstrate their skills, knowledge and understanding when studying for a qualification that meets their individual needs.

“The inclusion of controlled assessment and more varied question types will ensure that GCSEs continue to stretch and challenge young people.

“Ofqual will ensure that the GCSE standard is maintained.”

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